leetcode-196-Delete-Duplicate-Emails

描述


Write a SQL query to delete all duplicate email entries in a table named Person, keeping only unique emails based on its smallest Id.

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+----+------------------+
| Id | Email |
+----+------------------+
| 1 | john@example.com |
| 2 | bob@example.com |
| 3 | john@example.com |
+----+------------------+
Id is the primary key column for this table.

For example, after running your query, the above Person table should have the following rows:

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+----+------------------+
| Id | Email |
+----+------------------+
| 1 | john@example.com |
| 2 | bob@example.com |
+----+------------------+

分析


大意是删掉 Emails 表中 Email 重复的部分,留下 Id 最小的行

解决方案(MySQL)


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# Write your MySQL query statement below
DELETE
FROM
Person WHERE Id not in
(SELECT Id FROM
(SELECT min(Id) as Id FROM Person p GROUP BY p.Email) as tmp_table
)

题目来源